/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.smartandroid.sa.json;

import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.Collection;

import com.smartandroid.sa.json.internal.$Gson$Preconditions;

/**
 * A {@link FieldNamingStrategy2} that ensures the JSON field names begins with
 * an upper case letter.
 * 
 * <p>
 * The following is an example:
 * </p>
 * 
 * <pre>
 * class StringWrapper {
 * 	public String stringField = &quot;abcd&quot;;
 * 	public String _stringField = &quot;efg&quot;;
 * }
 * 
 * ModifyFirstLetterNamingPolicy policy = new ModifyFirstLetterNamingPolicy(
 * 		LetterModifier.UPPER);
 * String translatedFieldName = policy.translateName(StringWrapper.class
 * 		.getField(&quot;stringField&quot;));
 * 
 * assert (&quot;StringField&quot;.equals(translatedFieldName));
 * 
 * String translatedFieldName = policy.translateName(StringWrapper.class
 * 		.getField(&quot;_stringField&quot;));
 * 
 * assert (&quot;_StringField&quot;.equals(translatedFieldName));
 * </pre>
 * 
 * @author Joel Leitch
 */
final class ModifyFirstLetterNamingPolicy extends RecursiveFieldNamingPolicy {

	public enum LetterModifier {
		UPPER, LOWER;
	}

	private final LetterModifier letterModifier;

	/**
	 * Creates a new ModifyFirstLetterNamingPolicy that will either modify the
	 * first letter of the target name to either UPPER case or LOWER case
	 * depending on the {@code modifier} parameter.
	 * 
	 * @param modifier
	 *            the type of modification that should be performed
	 * @throws IllegalArgumentException
	 *             if {@code modifier} is null
	 */
	ModifyFirstLetterNamingPolicy(LetterModifier modifier) {
		this.letterModifier = $Gson$Preconditions.checkNotNull(modifier);
	}

	@Override
	protected String translateName(String target, Type fieldType,
			Collection<Annotation> annotations) {
		StringBuilder fieldNameBuilder = new StringBuilder();
		int index = 0;
		char firstCharacter = target.charAt(index);

		while (index < target.length() - 1) {
			if (Character.isLetter(firstCharacter)) {
				break;
			}

			fieldNameBuilder.append(firstCharacter);
			firstCharacter = target.charAt(++index);
		}

		if (index == target.length()) {
			return fieldNameBuilder.toString();
		}

		boolean capitalizeFirstLetter = (letterModifier == LetterModifier.UPPER);
		if (capitalizeFirstLetter && !Character.isUpperCase(firstCharacter)) {
			String modifiedTarget = modifyString(
					Character.toUpperCase(firstCharacter), target, ++index);
			return fieldNameBuilder.append(modifiedTarget).toString();
		} else if (!capitalizeFirstLetter
				&& Character.isUpperCase(firstCharacter)) {
			String modifiedTarget = modifyString(
					Character.toLowerCase(firstCharacter), target, ++index);
			return fieldNameBuilder.append(modifiedTarget).toString();
		} else {
			return target;
		}
	}

	private String modifyString(char firstCharacter, String srcString,
			int indexOfSubstring) {
		return (indexOfSubstring < srcString.length()) ? firstCharacter
				+ srcString.substring(indexOfSubstring) : String
				.valueOf(firstCharacter);
	}
}
